This invention generally relates to a workpiece holding-down device for a sewing machine and more particularly, to a workpiece holding-down device for a sewing machine which can automatically position the presser foot in a predetermined or desired position in response to the actuation of an operator's operation member such as the pedal or in accordance with a stored information.
In a sewing machine, it has been generally known that a workpiece to be processed is held against the table of the sewing machine by the presser foot under a suitable pressure.
In one of the conventional sewing machines, the presser foot is capable of moving between two predetermined positions, that is, the workpiece holding-down position in which the workpiece is pinched between the presser foot and the sewing machine table and the workpiece release position in which the presser foot is positioned above the workpiece on the sewing machine table, but can not be held in any intermediate position between the workpiece holding-down and release positions. Thus, the position of the presser foot can not be adjusted in accordance with the thickness of the workpiece to be processed. Therefore, in order to firmly or properly hold a workpiece having a very thin thickness down against the sewing machine table, a skilled operator is required. For example, when a new workpiece is manually fed to and held at the sewing area on the table of a sewing machine, if the distance between the presser foot in the workpiece release position and the workpiece is excessively great, the operator encounters difficulty in guessing which area or part of the workpiece will be engaged by the descending presser foot. Furthermore, the workpiece tends to slip off the sewing area on the sewing machine table during the time space from the time when the presser foot begins to descend to the time when the presser foot abuts against the upper surface of the workpiece. In order to solve the difficulty, the presser foot has to be moved upwardly and downwardly many times until the workpiece can be precisely set in a predetermined proper sewing position resulting in quite low operation efficiency.